Drought Stressed Lawns

Turf grass plants are 70% to 75% water, which indicates the importance of moisture in maintaining a vigorous, healthy, growing plant. When grasses lose more water through the leaves than they absorb through the root system, the plants become stressed.

The early stages of drought stress are seen as turf grass changing colors from bright green to a dull gray or blue-green color. Footprints and lawn mower wheel track remain for a period of time and the grass does not spring back upright. As plants begin to wilt the grass blades roll or fold. With additional stress, the turf loses its green color and becomes yellow, then tan. A tan color indicates drought dormancy.

Grass plants that are in drought stress are often damaged by foot traffic and mowing. Do not mow lawns that are in drought stress. The grass is not growing, and the plants have less moisture content to protect the cellular structure from collapse and permanent damage.

Broad leaf weeds and weedy grasses in drought stressed lawns may outgrow the turf and create an uneven appearance. However, even mowing the lawn at a high cutting height to cut off tall weeds may still result in lawn damage. When a lawn is dry, mower wheels often leave stripes across the lawn when the grass blades are broken and damaged by the weight of the wheels.

Some turf grasses such as Bermuda grass and tall fecue have more tolerance of low moisture conditions than other grasses. Centipede grass, bent grass, and annual blue grass are more prone to drought stress, and will lose green color quickly when soil moisture is low.

Heavy clay soils and sandy soils are not favorable for growing turf during periods of low moisture. The clay holds the moisture so tightly that grass roots cannot retrieve moisture, while sandy soils have a low moisture holding capacity.

Turf roots growing in thatch rather than in soil can result in a grass more prone to drought stress. Thatch is a layer of dead but undecomposed roots and stems above the soil. Thatch acts like a sponge. It quickly absorbs rainfall, but also dries out rapidly, leaving plant roots dry even after rainfall or watering.

Lawns mowed shorter than recommended for a grass type may have a shallow root system growing in the soil. A shallow root system dries quickly even when thatch is minimal.

Water the lawn once grass begins to discolor and wilt. If it is not possible to water sufficiently to keep grass green, water the lawn with at least 1/2 inch of water every 7 to 14 days. This light watering will help keep the plants alive even if they are dormant. Do NOT mow the lawn during hot weather when signs of drought stress are present.